In opthalmic surgery, following removal of the natural lens of the eye, an intraocular lens is implanted to take the place of the lens removed. Lenses designed to be placed in the posterior chamber may be implanted in either the ciliary sulcus or the capsular bag of the eye. Various types of such lenses have been proposed and are in use. For example, U.S. Pat. No. 4,159,546 discloses an intraocular lens supported by a plurality of flexible strands secured to the lens body. Another lens design is the so called "Simcoe Posterior Chamber Lens" sold by Cilco Inc. as their "S2" posterior chamber lens. The latter has long strands which gently curve from the point of connection to the free ends thereof.
Although great advances have been made over the years in intraocular lenses, the prior art designs are not without their problems. The Simcoe style prior art lenses (see FIG. 1) have very long, gently curving, loops which exert gentle pressure and are easily compressible, but, because of the length of the loops, the free ends thereof tend to move outwardly, i.e., away from the lens body, in response to compression. This type of lens, therefore, requires substantial intraocular manipulation to move it from the anterior chamber into position in the posterior chamber, so as to avoid injury to the delicate tissue in the eye, by the outwardly extending free ends of the haptics.
Each support strand of such prior art structure generally pivots about the point at which such support strand is anchored to the lens body, i.e., typically a point "P" on, or close to, the periphery of the lens body. Thus, generally radial pressure on the elongated seating portion of the support strands, such as is typically applied for manipulating the lens through the pupil and seating it in the posterior chamber, causes the free ends of the strands to move away from, or at least not toward, the lens body. Consequently, increased intraocular manipulation is required to move the lens, having these outwardly extending free ends of the haptics, into the posterior chamber without damaging the delicate membranes within the eye and it is particularly difficult to safely manipulate these outwardly extending free ends into the capsular bag.
U.S. Pat. No. 4,624,670, issued to Bechert on Nov. 25, 1986, discloses an intraocular lens having a pair of loops which extend from opposite sides of the lens body. Each of the loops includes a notch disposed generally mid-way along the curved seating portion of the loop in question. The notches are said to divide the seating portions so as to simulate a four-point fixation in the eye and at the same time facilitate insertion by reducing the possibility of slippage of the inserting instrument. The Bechert lens is shown to have haptics which pivot generally about their point of connection to the lens body, in response to compression of the haptic preparatory to seating thereof. The free ends of the haptics of Bechert, therefore, will move outwardly rather than inwardly with respect to the lens body in response to such compression.
If an effort is made to move the outwardly extending free ends of the haptics of such the prior art lenses toward the lens body, there is likely a substantial tendency for the lens body to rotate due to the location of the fulcrum, i.e., at the point of connection between the haptic and the lens body. Increased manipulation within the eye is therefore likely to be necessary in order to avoid such rotational movement of the lens body. Such added manipulation, of course, in addition to requiring substantial skill and being time consuming, increases also the risk of injury to the eye.
The present invention avoids these problems by allowing each lens support strand to be compressed toward the lens body by substantially the full amount required for moving the lens into the posterior chamber without resulting in an outward movement, i.e., a movement away from the periphery of the lens body, of the free ends of the lens support strands.
The lens support strands of the present invention preferably have long, gently curving, loops, but unlike those of the prior art, the loops of the present invention are provided with a weakened portion forming a second fulcrum located thereon at a location spaced from the lens body, i.e., intermediate the location at which the strand is anchored to the lens body (hereinafter "first fulcrum") and the elongated seating portion of the strand. The arrangement is such that the seating portion will, in response to generally radial compression thereof by the surgeon, pivot first about the intermediate "second" fulcrum and only finally (if additional compressive forces are exerted) about the first fulcrum. As noted above, the pivoting about such second fulcrum, of the haptics according to the present invention, avoids further outward movement of the free ends of the haptics during the initial compression of the haptics. This offers the advantages of allowing the surgeon to more readily position the lens without the lens body rotating about its axis and without the substantial risk of injury to the delicate tissue within the eye by outwardly extending distal portions of the haptics thus making such positioning and seating much simpler and safer.